What is this tiny spring?

I disassembled my LG GP65NB60 DVD reader/writer disc drive to see what was inside (just curious) this was my first time opening the drive and I foolishly unscrewed every screw thinking that they were holding the metal fixture down (only two of them were) then I also foolishly flipped the drive upside down to look at the other side.

As you can imagine, many pieces fell out, including the tiny spring you see in this photo on the blue mat to the right of the image.

This drive is internally very similar to this drive that there is an iFixit guide for. I was able to return everything to it's place, except for that one tiny spring I'm not certain of. I believe (thanks to the help of the iFixit AI chat bot) that it is an anti-backlash spring for the upper metal bolt of the slide assembly. I think I put it back in the right place, under the metal bolt at the top-right section (of the image) and the screw keeps it tight.

However, even though putting the drive back together in this way made it seem to function, it's not reading discs.

• The drive is recognized by my computer
• The drive ejects discs properly, both with software eject and with hardware button
• The disc spins when I put it in the drive
• I've tried multiple known-good discs, and multiple computers with multiple USB ports (Windows, Mac, Linux)

The drive thinks there is no disc in it. Does anyone know if I put the spring in the right place? If I did, does anyone know what could be causing everything but reading discs to work properly?